Management of wimax tones to avoid inter-modulation interference

ABSTRACT

Tones within WiMAX signals are disabled to eliminate interference at third-party receivers. A level of interference is determined between a base station transmitting a WiMAX signal and a third-party receiver. The level of interference is determined based at least on a characteristic of the third-party receiver and the WiMAX signal. One or more tones within the WiMAX signal are determined to disable at the base station to eliminate the interference. The tones are disabled prior to transmitting the WiMAX signal by the base station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/695,829, filed Apr. 3, 2007, entitled “Management Of Wi-Max Tones ToAvoid Inter-Modulation Interference,” which is herein incorporated byreference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

Base stations managed by wireless service providers transmitradio-frequency (RF) signals to support wireless communication sessionsof their subscribing mobile devices. These transmitted signals may causeinterference to nearby non-commercial (e.g. public safety) radioequipment that operates in the same or adjacent spectrum allocations.The interference can be intolerable if the non-commercial equipment ispart of public safety or critical infrastructure systems; such systemsare operated to provide emergency communications and, as such, generallycannot tolerate interference. The interference generally takes twoforms: out-of-band emissions (OOBE) from the base station transmitteritself, and intermodulation (IM) products formed in the first stages ofthe public-safety or other non-commercial receiver from therelatively-strong signals generated by the wireless base stationtransmitter.

Wireless service providers are obligated to correct interference topublic safety and other non-commercial systems that is caused by theirbase stations and other equipment. Correction of OOBE-relatedinterference can only be done by adding filtering at the wirelessservice provider's base station itself. Such filtering is readilyobtained, assuming the wireless provider's spectrum allocation iscontiguous (as is usually the case). Correction of IM-relatedinterference, on the other hand, can only be done through changing thebase station transmitter frequencies of operation. Such retuning ispractical for systems using a site-by-site channelization plan such asthe Integrated Digital Enhanced Network (iDEN). However, current modernwideband technologies, such as the Worldwide Interoperability forMicrowave Access (WiMAX) wireless service, do not allow for site-by-siteretuning plans. In fact, there currently does not exist a method formanipulating WiMAX signals in order to eliminate interference uponthird-party receivers caused by the WiMAX signals.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

The present invention is defined by the claims below. Embodiments of thepresent invention solve at least the above problems by providing asystem and method, and computer-readable media for, among other things,disabling tones within WiMAX signals in order to eliminate interferenceat third-party receivers.

In a first aspect, a system is provided for disabling tones within WiMAXsignals to eliminate interference at third-party receivers. The systemincludes a base station for transmitting WiMAX signals to mobiledevices. The system also includes an interference manager fordetermining an interference level between the base station and athird-party receiver, and for determining one or more tones within aWiMAX signal to disable at the base station. The interference level isdetermined based at least on characteristics of the third-party receiverand the WiMAX signal. Also included is a base station controller fordisabling the tones within the WiMAX signal transmitted by the basestation. The tones within the WiMAX signal are disabled prior totransmitting the WiMAX signal by the base station.

In a second aspect, a method is provided for disabling tones withinWiMAX signals to eliminate interference at third-party receivers. Alevel of interference is determined between a base station transmittinga WiMAX signal and a third-party receiver. The level of interference isdetermined based at least on a characteristic of the third-partyreceiver and the WiMAX signal. One or more tones within the WiMAX signalare determined to disable at the base station to eliminate theinterference. The tones within the WiMAX signal transmitted by the basestation are disabled prior to transmitting the WiMAX signal by the basestation.

In a third aspect, a method is provided for disabling tones within WiMAXsignals to eliminate interference at third-party receivers. The methodincludes determining a level of interference between a mobile devicetransmitting a WiMAX signal and a third-party receiver. The level ofinterference is determined based at least on a characteristic of thethird-party receiver and the WiMAX signal. One or more tones within theWiMAX signal are determined to disable at the mobile device to eliminatethe interference. The tones within the WiMAX signal transmitted by themobile device are disabled prior to transmitting the WiMAX signal by themobile device.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Illustrative embodiments of the present invention are described indetail below with reference to the attached drawing figures, which areincorporated by reference herein and wherein:

FIG. 1 is block diagram of an embodiment of a communication network thatcan be employed by the invention.

FIG. 2 is a block diagram of an exemplary system for implementing theinvention.

FIG. 3 is a block diagram of an embodiment of a interference manager.

FIG. 4 is a flow diagram of an embodiment of a method for disablingtones within WiMAX signals to eliminate interference to receivers causedby base stations.

DETAILED DESCRIPTION

Various technical terms are used throughout this description. Adefinition of such terms can be found in Newton's Telecom Dictionary byH. Newton, 21^(st) Edition (2005). These definitions are intended toprovide a clearer understanding of the ideas disclosed herein but arenot intended to limit the scope of the present invention. Thedefinitions and terms should be interpreted broadly and liberally to theextent allowed the meaning of the words offered in the above-citedreference.

As one skilled in the art will appreciate, embodiments of the presentinvention may be embodied as, among other things: a method, system, orcomputer-program product. Accordingly, the embodiments may take the formof a hardware embodiment, a software embodiment, or an embodimentcombining software and hardware. In one embodiment, the presentinvention takes the form of a computer-program product that includescomputer-useable instructions embodied on one or more computer-readablemedia.

Computer-readable media include both volatile and nonvolatile media,removable and nonremovable media, and contemplates media readable by adatabase, a switch, and various other network devices. Network switches,routers, and related components are conventional in nature, as are meansof communicating with the same. By way of example, and not limitation,computer-readable media comprise computer-storage media andcommunications media.

Computer-storage media, or machine-readable media, include mediaimplemented in any method or technology for storing information.Examples of stored information include computer-useable instructions,data structures, program modules, and other data representations.Computer-storage media include, but are not limited to RAM, ROM, EEPROM,flash memory or other memory technology, CD-ROM, digital versatile discs(DVD), holographic media or other optical disc storage, magneticcassettes, magnetic tape, magnetic disk storage, and other magneticstorage devices. These memory components can store data momentarily,temporarily, or permanently.

Communications media typically store computer-useableinstructions—including data structures and program modules.Communications media include any information-delivery media. By way ofexample but not limitation, communications media include wired media,such as a wired network or direct-wired connection, and wireless mediasuch as acoustic, infrared, radio, microwave, spread-spectrum, and otherwireless media technologies. Combinations of the above are includedwithin the scope of computer-readable media.

FIG. 1 is a block diagram of an embodiment of a communication network100 that can be employed by the invention. Mobile device 102 may be orcan include a laptop computer, a network-enabled mobile telephone (withor without media capturing/playback capabilities), a wireless emailclient, a personal digital assistant (PDA), or other software client.The mobile device 102 may also include a machine or device to performvarious tasks including video conferencing, web browsing, search,electronic mail (email) and other tasks, applications and functions.Mobile device 102 may additionally be a portable media device such asdigital camera devices, digital video cameras (with or without stillimage capture functionality), media players such as personal musicplayers and personal video players, and other portable media devices.The mobile device 102 can include a communication interface that canallow the mobile device 102 to transmit information via radio signals toa communication tower 104.

The Base Station (BS) 106 contains equipment for transmitting andreceiving of radio signals from a communication tower 104. BS 106 alsohas other equipment for encrypting and decrypting communication with theBase Station Controller (BSC) 108. The BSC 108 may be configured toreceive radio signals that are converted into Time Division Multiplexing(TDM) from a BS 106. In an embodiment, the BSC 108 can have a pluralityof BSs under its control. The BSC 108 may handle the allocation of radiochannels, may receive measurements from mobile devices, and can controlhandovers from one BS to another BS. Another function of the BSC 108 isto act as a concentrator of communication sessions where many differentlow capacity connections to the BSs (with relatively low utilization)become reduced to a smaller number of connections towards a MobileSwitching Center (MSC) (with a high level of utilization). The BSC mayalso be configured to send voice information from the TDM signal to theMSC and data information to an Access Service Network (ASN) or a PacketData Serving Node (PDSN) 110.

The ASN/PDSN 110 may be a component of a mobile network. The ASN/PDSN110 may act as a connection point between the Radio Access and InternetProtocol (IP) networks. The ASN/PDSN 110 component may be responsiblefor managing Point-to-Point Protocol (PPP) sessions between the mobiledevice's core IP network and the mobile device. The Home Agent (HA) 112may be a router located in a home network of the mobile device 102. TheHA 112 allows a mobile device to connect to the Internet or data networkby assigning an IP address and binding it to a Care-of-Address (COA).The HA 112 can forward packets to an appropriate network when a mobiledevice is away from its home area or home network. An authentication,authorization, and accounting (AAA) server 114 is a server program thathandles user requests for access to a network and provides AAA services.The AAA server 114 may interact with network access servers, gatewayservers, databases, and directories containing user information. ASession Border Controller (SBC) 116 may be a device used in some Voiceover Internet Protocol (VoIP) networks to exert control over thesignaling and media streams involved in setting up, conducting, andtearing down calls. The SBC 116 may be put into the signaling and/ormedia path between the party making a call and the party receiving thecall. In an embodiment, the SBC 116 may act as a VoIP phone when itreceives a call from a calling party, and can place a second call to thecalled party. The effect of this behavior may be that the signalingtraffic and media traffic (voice, video, etc.) crosses the SBC. Thisbehavior may also be prevalent during conference communications.

FIG. 2 is a block diagram of an exemplary system 200 for implementingthe invention. The system includes BSC 202, interference manager 204, BS206, and network 208. In an embodiment, BSC 202, interference manager204, BS 206, and network 208 may be managed by the same wirelesscommunication service provider. In an embodiment, the wirelesscommunication service provider may be configured to provide WorldwideInteroperability for Microwave Access (WiMAX) wireless service tosubscribing mobile devices. In such an embodiment, BS 206 may transmit aplurality of WiMAX signals to subscribing mobile devices during eachmobile device's communication session. Each WiMAX signal may comprise aplurality of individual WiMAX frequencies. These individual frequenciesare called tones. A BS 206 may be a potentially interfering BS when itstransmitted WiMAX signals have the potential to interfere with athird-party receiver such as receiver 208. In an embodiment, a BS 206 isa potentially interfering BS if it is located in a geographic locationthat is near the receiver 208. A BS 206 can be considered to be in ageographic location that can potentially interfere with the receiver 208if the BS 206 and receiver 208 are located in the same state, city, orwithin a predetermined distance away from each other.

Receiver 208 is a receiver that has the potential to be interfered withby WiMAX signals transmitted by BS 206. Receiver 208 may be a receiverused with, for example, public safety radios, radios of utilities suchas power companies and gas companies, and radios used by other wirelesscommunication service providers. In an embodiment, receiver 208 may be areceiver that operates within an 800 megahertz spectrum or otherfrequency spectrum.

BSC 202 is utilized to disable certain tones within WiMAX signalstransmitted at certain BSs 206 in order to eliminate interference uponreceivers 208 caused by the transmitted WiMAX signals. BSC 202 can useinterference manager 204 to determine which BSs 206 are causing aninterference and which tones to disable within WiMAX signals transmittedby the BSs 206 to eliminate the interference. Interference manager 204may be or can include a server or computing device such as a workstationrunning Microsoft Windows®, MacOS™, Unix™ Linux, Xenix™, IBM AIX™,Hewlett-Packard UX™, Novell Netware™, Sun Microsystems Solaris™, OS/2™,BeOS™, Mach™, Apache™, OpenStep™ or other operating system or platform.To determine which tones to disable at the base stations, theinterference manager will need to be informed of certain information.This information includes, but is not limited to, the signal desired tobe received at the receiver 208, the characteristics of the receiver208, the WiMAX signals transmitted by the BS 206, and the interferencelevel created upon the receiver by the BS 206. In an embodiment,interference manager 204 is a component within BSC 202.

FIG. 3 is a block diagram of an embodiment of an interference manager300. Interference manager 300 includes interference calculator 302 andtone calculator 304. Interference calculator 302 is used to calculatethe interference level created upon the receiver 206 by BS 206. Theinterference level is used to represent the strength of the interferenceupon the receiver 206 that is caused by the BS 206. The interferencecalculator may employ a conventional interference-determining algorithmto calculate the interference level. In order for the interferencecalculator 302 to calculate the interference level, certain informationmust be inputted into the interference calculator. This informationincludes, but is not limited to, the frequency and level of the desiredsignal to be received (and which therefore requires protection) at thereceiver 208, the characteristics of the receiver 208, and the WiMAXsignal transmitted by the BS 206 as received at receiver 208. Thefrequency and level of the desired signal to be received at receiver 208may be determined by an entity managing the receiver 208 such as apublic safety or other non-commercial entity for example. Such an entitymay provide the interference manager 300 with the desired signal thatneeds to be protected for its receiver 208. Once the desired signal isreceived, it may be inputted into the interference calculator 302 forprocessing.

The characteristics of the a receiver 208 may include, but are notlimited to, the reference sensitivity of the receiver, aninter-modulation rejection ratio of the receiver, and whether there is afiltering mechanism within the receiver that adjusts the level ofpotential interferers. The characteristics of the receiver 208 may alsobe provided by the entity managing or that manufactured the receiver208. In an embodiment, the characteristics of the receiver may bemeasured and provided by an entity other than the entity managing thereceiver 208. The WiMAX signals transmitted by a potentially interferingBS 206 may also be measured. In another embodiment, the WiMAX signalstransmitted by the BS may be estimated using a conventional interferenceestimation model. Once the characteristics of the receiver 208 and theWiMAX signals are received, they are both inputted into the interferencecalculator for processing.

The interference calculator 302 can use the conventionalinterference-determining algorithm to calculate the interference levelbetween the receiver 208 and one or more BSs 206. Again, theinterference level will be calculated based on the inputted elementsincluding the desired signal to be received at the receiver 208, thecharacteristics of the receiver 208, and the WiMAX signal transmitted bythe BS 206. For IM interference to become an issue, two things have tohappen: (a) The frequency of the IM product must fall within the channelbandwidth of the desired signal, and (b) the level of the IM productmust be sufficiently strong to lower the ratio of desired signal to allinterference and noise below the minimum for the desired signal to berecovered correctly in receiver 208. The characteristics of the receiver208 and the relative signal streams of WiMAX signals transmitted by theBS 206 arriving at the receiver determine how strong the interference ofthe WiMAX signals is going to be on the receiver 208. The interferencecalculator 302 can be configured to output a textual or graphicalrepresentation that informs a user of the interference level caused bythe BS 206.

Once the interference level between the BS 206 and the receiver 208 hasbeen determined, the tone calculator 304 can be utilized to determinewhich tones to disable within the WiMAX signals transmitted by the BS206 to eliminate the interference. The tone calculator may be equippedwith an algorithm that can determine which tones to disable based onelements including, but not limited to, the interference level betweenthe BS 206 and the receiver 208, the desired signal to be received atthe receiver 208, the characteristics of the receiver 208, and the WiMAXsignals transmitted by the BS 206. These elements are inputted into thealgorithm and the algorithm outputs which tones to disable at the BS 206in order to eliminate the interference. The algorithm can determinewhich tones to disable for a plurality of interfering BSs 206. When aplurality of BSs 206 are involved, the algorithm can determine whichtones to disable on a site-by-site basis, meaning that it can determinewhich set of tones need to be disabled at specific BSs 206. In such anexample, the algorithm may determine that a first set of tones need tobe disabled at a first BS 206, while a second set of tones that aredifferent from the first set should be disabled at another BS 206 toeliminate the overall interference.

Every time a tone is disabled at a BS, the BS loses some capacity toprocess data related to wireless communication sessions of itssubscribing mobile devices. Accordingly, the algorithm can be configuredto disable a minimum number of tones at each BS 206 to eliminate theinterference problem at the receiver 206 while maintaining apredetermined capacity level at the BS. In another embodiment, thealgorithm can be configured to determine if it is necessary to eliminatetones transmitted at certain mobile devices supported by the BS 206.This may be necessary in instances when the desired signals to bereceived at the receiver are suddenly changed, or if some othercontributors in the area around either the mobile device, BS 206, orreceiver 208, are suddenly changed in some way. In such an embodiment,the algorithm can determine which tones should be disabled at whichspecific mobile devices. Once the tone calculator 304 determines whichtones to disable, the interference manager 300 can inform the BSC 202 ofwhich tones it needs to disable at the corresponding BSs 206. With thatinformation, the BSC 202 can proceed to disable the specified tones. Inthe embodiment in which tones need to be disabled at the mobile device,the interference manager 300 can inform the BSC 202 of which tones needto be disabled at which mobile devices, and the BSC 202 can proceed tocommand the mobile device to disable such tones.

FIG. 4 is a flow diagram of an embodiment of a method 400 for disablingtones within WiMAX signals to eliminate interference to receivers causedby base stations. At operation 402, signals desired to be received by areceiver that need to be protected from interference are identified. Inan embodiment, the desired signal that needs to be protected may beprovided by an entity managing the receiver. In an embodiment, thedesired signal may be measured. In yet another embodiment, the desiredsignal is the frequency at which the receiver operates. At operation404, characteristics of the receiver are identified. In an embodiment,the characteristics of the receiver may be provided by the entity thatmanages or that manufactured the receiver. In another embodiment, thecharacteristics may be measured by an entity. At operation 406, WiMAXsignals transmitted by potentially interfering BSs are identified. Thesesignals may be estimated or measured. At operation 408, the interferencelevel of the transmitted WiMAX signals at the receiver are determined.In an embodiment, the interference level is determined by aninterference manager such as interference manager 300 and is based onthe signal desired to be received at the receiver, the characteristicsof the receiver, and the WiMAX signals transmitted by the BS. Atoperation 410, a list of tones that need to be disabled at theinterfering BSs (the potentially interfering BSs that have beendetermined to interfere with the receiver) are provided. In anembodiment, the list is provided by the interference manager. Atoperation 412, the list of tones is received. In an embodiment, the listis received by a BSC. At operation 414, the specified tones on the listare disabled at the corresponding BSs. In an embodiment, the BSC willdisable the tones.

Many different arrangements of the various components depicted, as wellas components not shown, are possible without departing from the spiritand scope of the present invention. Embodiments of the present inventionhave been described with the intent to be illustrative rather thanrestrictive. Alternative embodiments will become apparent to thoseskilled in the art that do not depart from its scope. A skilled artisanmay develop alternative means of implementing the aforementionedimprovements without departing from the scope of the present invention.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations and are contemplated within the scope of the claims. Notall steps listed in the various figures need be carried out in thespecific order described.

The invention claimed is:
 1. A system for disabling tones within WiMAXsignals to eliminate interference at third-party receivers, comprising:a base station for transmitting WiMAX signals to mobile devices; aninterference manager for determining an interference level between thebase station and a third-party receiver, and for determining one or moretones within a WiMAX signal to disable at the base station, wherein theinterference level is determined based at least on one or more signalsthat need to be protected at the third-party receiver and oncharacteristics of the third-party receiver and the WiMAX signal,wherein an algorithm determines the one or more tones to disable basedon the interference level, the one or more protected signals, and thecharacteristics of the third-party receiver and the WiMAX signal; and abase station controller for disabling the one or more tones within theWiMAX signal transmitted by the base station, wherein the one or moretones within the WiMAX signal are disabled prior to transmitting theWiMAX signal by the base station.
 2. The system according to claim 1,wherein the interference manager determines one or more tones to disablein at least one mobile device.
 3. The system according to claim 2,wherein the determined one or more tones are a minimum number of tonesneeded to eliminate the interference level and to maintain apredetermined level of capacity at the base station.
 4. A method ofdisabling tones within WiMAX signals to eliminate interference atthird-party receivers, comprising: determining a level of interferencebetween a base station transmitting a WiMAX signal and a third-partyreceiver, wherein the level of interference is determined based at leaston a characteristic of the third-party receiver, a signal to beprotected at the third-party receiver, and the WiMAX signal; determiningone or more tones within the WiMAX signal to disable at the base stationto eliminate the interference, based on the level of interference, thesignal to be protected, the characteristic of the third-party receiver,and the WiMAX signal; disabling the one or more tones within the WiMAXsignal transmitted by the base station, wherein the one or more toneswithin the WiMAX signal are disabled prior to transmitting the WiMAXsignal by the base station.
 5. The method according to claim 4, whereinthe interference is interference that forms in the third-party receiver.6. The method according to claim 4, wherein the characteristic of thethird-party receiver includes at least one of a reference sensitivity ofthe third-party receiver, an inter-modulation rejection ratio of thethird-party receiver, or a filtering mechanism within the third-partyreceiver.
 7. The method according to claim 4, wherein the one or moretones are disabled by a base station controller.
 8. The method accordingto claim 4, wherein the one or more tones include a minimum number oftones to eliminate the interference level and to maintain apredetermined level of capacity at the at least one base station.
 9. Amethod of disabling tones within WiMAX signals to eliminate interferenceat third-party receivers, comprising: determining a level ofinterference between a WiMAX signal and a third-party receiver, whereinthe level of interference is determined based at least on acharacteristic of the third-party receiver, a signal to be protected atthe third-party receiver, and the WiMAX signal; determining one or moretones within the WiMAX signal to disable at a mobile device to eliminatethe interference, based on the level of interference, the signal to beprotected, the characteristic of the third-party receiver, and the WiMAXsignal; disabling the one or more tones within the WiMAX signaltransmitted by the mobile device, wherein the one or more tones withinthe WiMAX signal are disabled prior to transmitting the WiMAX signal bythe mobile device.
 10. The method according to claim 9, wherein theinterference is interference that forms in the third-party receiver. 11.The method according to claim 9, wherein the characteristic of thethird-party receiver includes at least one of a reference sensitivity ofthe third-party receiver, an inter-modulation rejection ratio of thethird-party receiver, or a filtering mechanism within the third-partyreceiver.
 12. The method according to claim 9, wherein the one or moretones within the WiMAX signal are disabled by utilizing a base stationcontroller to instruct the mobile device to disable the one or moretones.